Abstract
BackgroundExercise intolerance, desaturation, and dyspnea are common features in patients with chronic obstructive pulmonary disease (COPD). At altitude, the barometric pressure (BP) decreases, and therefore the inspired oxygen pressure and the partial pressure of arterial oxygen (PaO2) also decrease in healthy subjects and even more in patients with COPD. Most of the studies evaluating ventilation and arterial blood gas (ABG) during exercise in COPD patients have been conducted at sea level and in small populations of people ascending to high altitudes. Our objective was to compare exercise capacity, gas exchange, ventilatory alterations, and symptoms in COPD patients at the altitude of Bogotá (2,640 m), of all degrees of severity.MethodsMeasurement during a cardiopulmonary exercise test of oxygen consumption (VO2), minute ventilation (VE), tidal volume (VT), heart rate (HR), ventilatory equivalents of CO2 (VE/VCO2), inspiratory capacity (IC), end-tidal carbon dioxide tension (PETCO2), and ABG. For the comparison of the variables between the control subjects and the patients according to the GOLD stages, the non-parametric Kruskal–Wallis test or the one-way analysis of variance test was used.ResultsEighty-one controls and 525 patients with COPD aged 67.5 ± 9.1 years were included. Compared with controls, COPD patients had lower VO2 and VE (p < 0.001) and higher VE/VCO2 (p = 0.001), A-aPO2, and VD/VT (p < 0.001). In COPD patients, PaO2 and saturation decreased, and delta IC (p = 0.004) and VT/IC increased (p = 0.002). These alterations were also seen in mild COPD and progressed with increasing severity of the obstruction.ConclusionThe main findings of this study in COPD patients residing at high altitude were a progressive decrease in exercise capacity, increased dyspnea, dynamic hyperinflation, restrictive mechanical constraints, and gas exchange abnormalities during exercise, across GOLD stages 1–4. In patients with mild COPD, there were also lower exercise capacity and gas exchange alterations, with significant differences from controls. Compared with studies at sea level, because of the lower inspired oxygen pressure and the compensatory increase in ventilation, hypoxemia at rest and during exercise was more severe; PaCO2 and PETCO2 were lower; and VE/VO2 was higher.
Highlights
Chronic obstructive pulmonary disease (COPD) is the most prevalent chronic respiratory disease worldwide, even in cities located at high altitudes, and is the main cause in both men and women of the highest number of deaths and disability-adjusted life-years attributable to these chronic diseases (Caballero et al, 2008; Horner et al, 2017; Collaborators, 2020)
Hemoglobin (Hb) values were significantly higher in the COPD patients at Global Initiative for Chronic Obstructive Pulmonary Disease (GOLD) stages 2–4 than controls (p < 0.001)
The main findings of this study, with a significant number of COPD patients residing at high altitude, were the following: (1) progressive decrease in exercise capacity, increased dyspnea, dynamic hyperinflation (DH), restrictive mechanical constraints, and gas exchange abnormalities during exercise, across GOLD stages
Summary
Chronic obstructive pulmonary disease (COPD) is the most prevalent chronic respiratory disease worldwide, even in cities located at high altitudes, and is the main cause in both men and women of the highest number of deaths and disability-adjusted life-years attributable to these chronic diseases (Caballero et al, 2008; Horner et al, 2017; Collaborators, 2020). In studies at sea level in patients with mild COPD, it has been shown that during exercise, compared to healthy subjects, oxygen uptake (VO2) and work rate (WR) are lower, and ventilatory equivalents for CO2 (VE/VCO2) and the dead space–to–tidal volume ratio (VD/VT) are higher, with similar values of partial pressure of arterial oxygen (PaO2) and the alveolar–arterial oxygen tension gradient (A-aPO2) (Elbehairy et al, 2015). In Bogotá, a city located at high altitude (2,640 m, BP 560 mm Hg), the PaCO2 at rest in healthy subjects decreases to approximately 33 mm Hg, and the PaO2 is 65 mm Hg, with values less than 60 mm Hg in the elderly (GonzalezGarcia et al, 2020) and even lower values in COPD patients (Gonzalez-Garcia et al, 2004). The barometric pressure (BP) decreases, and the inspired oxygen pressure and the partial pressure of arterial oxygen (PaO2) decrease in healthy subjects and even more in patients with COPD. Our objective was to compare exercise capacity, gas exchange, ventilatory alterations, and symptoms in COPD patients at the altitude of Bogotá (2,640 m), of all degrees of severity
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
